1. Field of the Invention
This invention relates to providing a quiet hand-held hair dryer. More particularly, this invention concerns hair dryer configuration and component combinations for making the hair dryer exceptionally quiet and efficient.
2. Description of the Prior Art
Typically, a portable (hand-held) electric hair dryer has an elongated housing of insulating material which is provided with a handle and has an air-admitting inlet and an air-discharging outlet. A rotary impeller which is driven by an electric motor draws air into the housing by way of the air-admitting inlet and induces a flow of air toward the air-discharging outlet whereby the air stream passes along one or more electric heating elements. Typically, such portable hair dryers emit noise which is both loud and experienced as unpleasant. Some of the reasons for this noise are the following:
1) The typical internal configuration places the electric motor between the impeller and air-discharging outlet. This configuration limits the space available for air passage, necessitating a velocity of air flow at the impeller which is much faster than that experienced at the air-discharging outlet. In order to achieve this faster airflow, the motor must operate at very high revolutions per minute (18,000-20,000). At this high speed, the electric motors emit a sound which is experienced by users as being both loud and irritating.
2) The electric motor is typically pressed into a casing which is integral to the housing and secured with machine screws. As a result, the housing amplifies the vibrations of the motor by converting mechanical energy of the motor to sound energy.
3) The noise emitted by electric motors is typically left undampened, leaving the motor noise an unobstructed passage to the user's ear.
4) The air-admitting inlet, through which much of the high frequency sound escapes, is usually positioned in the back of the hair dryer--which points the high frequency noise emission at salon users, or it is on the side of a hair dryer--which faces the high frequency emission at both salon and home users.
5) The tip speed of the impeller is kept slower than optimal for a given motor speed due to impeller sizes typically measuring only two and a quarter inches across their diameter. Tip speed is also diminished in relation to motor speed by impeller blade designs which equalize the rate of airflow between the inside of an impeller blade and the outside of an impeller blade.
A hair blower design which addresses one or more of the above issues would reduce the noise output of a hand-held portable hair dryer. A hair dryer which successfully addresses all of these issues would substantially reduce the noise output. Inasmuch as hair dryers are appliances in daily use, which can only survive in the marketplace if they can be manufactured at attractive prices in large quantities utilizing the latest mass-production techniques, design improvements must be combined with the aim of achieving the desired improvements with minimal to no additional manufacturing costs. Typically, portable hair dryer patents which have addressed noise output have neglected the above design issues.